利用图像信息方法研究芦山M_S7.0地震前川滇及附近地区的图像异常

Anomalous seismic activities in the Sichuan--Yunnan region and its adjacent areas before the Lushan M_S7.0 earthquake by the pattern informatics method

图像信息方法是一种基于统计物理学的地震预测方法.该方法通过严格的统计检验给出地震活动状态显著偏离平均状态的地区(即显著平静或显著活跃的地区),称为"地震热点".以往研究结果表明该方法是一个预测效能较高的中长期地震预测方法.本文利用中国地震台网中心提供的1970年以来的地震目录,在剔除余震、选取完备震级的基础上,基于前期研究工作结果中预测效能较高的计算参数,即网格尺度为2°×2°、预测时间窗为9年,分析2008年汶川MS8.0地震后到2013年芦山MS7.0地震前川滇地区的图像信息演化过程.结果表明,2009—2010年间芦山MS7.0地震震中附近的鲜水河断裂带、龙门山断裂带和安宁河断裂带交汇区(29°—31°N,101°—105°E)存在明显的地震热点,2011—2012年该地震热点缩小至(29°—31°N,101°—103°E)范围,2012年以后消失,继而于2013年发生芦山MS7.0地震.本文还对比研究了网格尺度为1°×1°时的图像信息演化过程,结果显示2009—2010年芦山地震附近的新津—成都—德阳断裂南部、龙泉山西缘断裂南段、马边—盐津断裂带、峨边断裂带、天全—萦经断裂带(29°—30°N,103°—104°E)也出现过地震热点,2011年以后该热点消失,2013年发生芦山MS7.0地震.本文讨论了计算参数对预测结果的影响,并根据目前存在的地震热点分析了川滇及附近地区今后强震发生的可能地点.

The Pattern Informatics （PI ）method is a new approach for earth-quake prediction based on statistical physics.This method can detect the re-gions where seismicity significantly deviates from the normal state （i.e.,seismic quiescence or seismic activation）,known as “seismic hotspots”,via strict sta-tistical tests.Previous results show that PI is effective for medium- to long-term earthquake prediction.In this paper,after declustering and choosing complete-ness magnitude,the PI method was applied to earthquake catalogue from China Earthquake Networks Center since 1970,to detect the existence of seismic hotspots before the Lushan MS7.0 earthquake on April 20,2013.Based on suit-able parameters （with grid size of 2°×2°and forecast window of 9 years）with higher prediction efficiency according to the previous researches of western Chi-na,we obtained the evolution of PI anomaly during the period from Wenchuan MS8.0 earthquake to Sichuan Lushan MS7.0 earthquake.The results showed that obvious seismic hotspots appeared in the convergent region （29°-31°N, 101°-105°E）of the Xianshuihe,Longmenshan and An’ninghe faults from 2009 to 2010.These seismic hotspots shrank to the range of （29°-31°N,101°-103° E）during the years of 2011-2012 and disappeared after 2012,then the 2013 Lushan MS 7 .0 earthquake occurred.In another evaluation of the evolution of PI anomaly by using a different set of calculation parameters （with grid size of 1°× 1°and forecast window of 9 years）,the results showed that there was a hotspot from 2009 to 2010 covering the southern Xinjin--Chengdu--Deyang fault,south-ern segment of Longquanshan western edge fault,Mabian--Yanjin fault,Ebian fault,and Tianquan--Yingjing fault （29°-30°N,103°-104°E）.After 2011, this hotspot disappeared and the Lushan MS7.0 earthquake occurred in 2013. We also discussed the potential seismic risk in the studied area as well as the in-fluence of calculated parameters on the prediction efficiency.